The present invention relates to high-field permanent magnets. More specifically, it relates to permanent magnet structures that provide internal uniform magnetic fields that can be accessed through non-distorting access ports.
One of the most critical problems confronting designers of high-intensity internal magnetic field sources has been accessing the internal field without distorting it. More specifically, those skilled in the art know that drilling an access port in the shell of a magnetic structure that produces an internal magnetic field can significantly distort the uniformity of that internal field, and thus severely limit the usefulness of the structure. The following references show many types of magnetic structures that can be utilized for such purposes:
Leupold, U.S. Pat. No 4,835 506 issued 30 May 1989, entitled "Hollow Substantially Hemispherical Permanent Magnet High-Field Flux Source;"
Leupold, U.S. Pat. No. 4,837,542, issued 6 Jun. 1989, entitled "Hollow Substantially Hemispherical Permanent Magnet High-Field Flux Source for Producing a Uniform High Field;"
Leupold, U.S. Pat. No. 4,839,059, issued 13 Jun. 1989, entitled "Clad Magic Ring Wigglers;"
Leupold, U.S. Statutory Invention Registration H591, published 7 May 1989, entitled "Method of Manufacturing of a Magic Ring;"
Leupold et al., "Novel High-Field Permanent-Magnet Flux Sources," IEEE Transactions on Magnetics, vol. MAG-23, No. 5, pp. 3628-3629, September 1987;
Leupold et al., "A Catalogue of Novel Permanent-Magnet Field Sources," Paper No. W3.2, 9th International Workshop on Rare-Earth Magnets and Their Applications, pp 109-123, August 1987, Bad Soden, FRG;
Leupold et al, "Design applications of magnetic mirrors," Journal of Applied Physics, 63(8), 15 Apr. 1988, pp. 3987-3988; Leupold et al, "Applications of yokeless flux confinement," Journal of Applied Physics, 64(10), 15 Nov. 1988, pp. 5994-5996; and
Abele et al., "A general method for flux confinement in permanent-magnet structures," Journal of Applied Physics, 64(10), 15 Nov. 1988, pp. 5988-5990.
Leupold, U.S. Pat. No. 5,103,200, issued 7 Apr. 1992, entitled "High-Field Permanent Magnet Flux Source."
These references show many different permanent-magnet structures. Each structure having a permanent magnet shell that produces a uniform magnetic field of unusually high intensity in an internal cavity. Holes are drilled through the shell to form ports through which the internal field can be accessed. Drilling the port holes, however, removes critical magnetic material from the shell, thus disrupting the uniformity of the shell's magnetization which, in turn, distorts the uniformity of the internal field. Consequently, such structures are unacceptable for high precision applications.
One solution to this distortion problem was recently described by the present inventor in U.S. Pat. No. 5,216,401, entitled, MAGNETIC FIELD SOURCES HAVING NON-DISTORTING ACCESS PORTS, issued 1 Jun. 1993, and incorporated herein by reference. This patent discloses structures having a permanent magnet shell that produces an internal uniform magnetic field accessed through non-distorting ports drilled in predetermined regions of the shell. The amount of material needed to construct the shell, however, is minimized as compared to the prior art, and thus the overall size and weight of these structures is significantly reduced. In order to minimize the amount of material comprising the shell and still provide access ports to the internal uniform magnetic field without distorting that field, the remanence of the shell is varied as a function of the polar angle around the shell. As a result, to construct such a remanence-varying shell, the artisan is required to have access to and assemble many different permanent magnets. Thus, it is difficult, time-consuming and costly to construct these structures.
Consequently, this technique is undesirable for those who do not have the resources nor the time necessary to complete this formidable time consuming task. As a result, those skilled in the art would welcome a simplified method of constructing such magic sphere and magic ring structures.